In recent years, Bluetooth (registered trademark) is gaining attention as a means for short range wireless communications, and various enabled devices are developed and sold.
In Bluetooth communications, in starting communications, a search message for detecting devices existing in the vicinity is broadcast from a device (Bluetooth device) called a master, which controls communications, and a device which responds to that message is detected as a slave that is able to communicate with the master.
FIG. 1 is a diagram showing an example of device arrangement. In addition, FIG. 2 is a flow chart illustrating a search process performed by each of the devices in FIG. 1.
A searcher device 1 is, for example, a device that is in use by a user, and searchee devices 11 through 13 are devices that exist in the vicinity (within a range reachable by signals) of the searcher device 1.
In FIG. 1, if the user instructs the searcher device 1 to search for devices capable of communications, a search for devices existing within a predetermined range, with the searcher device 1 as the center, is performed.
In other words, in step S1 in FIG. 2, an inquiry packet, which is the search message, is broadcast by the searcher device 1, and that is received by the searchee devices 11 and 12 in steps S11 and S21, respectively. In addition, in FIG. 1, the search range of the searcher device 1 (the range reached by the signals used for transmitting the inquiry packet) is indicated with a circle in broken lines with the searcher device 1 as the center, and the searchee device 13 is outside thereof. Therefore, the inquiry packet broadcast by the searcher device 1 is not received by the searchee device 13.
In steps S12 and S22, the searchee devices 11 and 12, respectively, that received the inquiry packet transmit to the searcher device 11 a response message (FHS packet) with respect to the inquiry packet. Information, such as the Bluetooth device name, a Bluetooth address that is set as something unique to each Bluetooth device, a Bluetooth clock for achieving the synchronization of time slots for frequency hopping and the like, is included in this FHS packet.
In steps S2 and S3, the searcher device 1 receives the FHS packets transmitted from the searchee devices 11 and 12, presents the Bluetooth device names or the like included therein to the user and makes him select a device with which communications is to be established.
In other words, ordinarily, the user needs to select from a list of devices presented as existing in the vicinity a device with which communications is to be established.
As such, as a technology for automatically establishing communications and having the device itself specify a communications partner without making the user make such a selection, there is something like the one disclosed in Japanese Unexamined Patent Application Publication No. 2001-156704 (hereinafter referred to as Patent Document 1).
In Patent Document 1, there is disclosed a technology where the intensity of signals transmitted from a plurality of devices detected through a search is each detected, and the device that transmits the signal with the highest intensity is specified as a communications partner device. Since a communications establishment process that ensues is performed automatically with the device that is specified as a communications partner, the user is able to establish communications with that device by merely bringing his own device closer to the device that is to be the communications partner.
However, with the technology disclosed in Patent Document 1, there is a problem in that since the device transmitting signals of the highest intensity is selected as a communications partner device, depending on objects in the surroundings that reflect radio waves or on communications characteristics of the detected devices, communications are sometimes initiated automatically with a device other than the device with which the user is trying to initiate communications.
In other words, the range and intensity of signals of each of the devices do vary to some extent, and it is not necessarily the case that the signal with the highest intensity would be received from the device at the closest location.